How to Unblock an Outside Drain: UK Step-by-Step Guide

Blocked outside drains are among the most common drainage problems in UK homes — and one of the most straightforward to tackle yourself if you catch them early. Water pooling on a patio, overflow from a gully, or a persistent bad smell from an external drain are all signs worth acting on quickly. Here is the complete step-by-step guide for clearing an outside drain in the UK.

What is an Outside Drain?

Your property's external drainage system collects surface water (rain, patio runoff) and waste water from appliances such as washing machines, kitchen sinks, and dishwashers. These drains run into gully pots — square or round chambers set into the ground — which connect to the underground drain network.

Most outside drain blockages occur at two points: at the gully grate (the removable grid at the surface) and inside the gully pot below it. Leaves, moss, soil, and cooking grease build up at these points over time. Deeper blockages in the underground pipe require more intervention.

Step 1: Identify Where the Blockage Is

Before you begin, work out where the problem is:

• Is only one gully blocked, or are multiple external drains running slowly?
• Is the gully pot full of standing water, or is it backing up despite appearing clear at the surface?
• Is there a sewage smell, suggesting foul water is involved as well as surface water?

If only one gully is affected, the blockage is likely in or just below that specific gully. If multiple drains are slow simultaneously, the blockage is probably further downstream in a shared drain run.

Step 2: Remove the Gully Grate and Clear Visible Debris

Put on rubber gloves. Lift the gully grate and remove all accumulated debris — leaves, matted silt, moss, decomposing organic matter, or food grease on kitchen drains. Dispose of it in your general waste bin. This step alone clears a significant proportion of outside drain blockages in UK gardens and patios.

After clearing the surface, flush the gully with a bucket of water to see whether it drains freely.

Step 3: Clear Inside the Gully Pot

With the grate removed, look down into the gully pot. If it is full of water or sediment, scoop out standing water with a jug and remove accumulated material with a gloved hand or garden trowel. Pay close attention to the outlet at the bottom of the pot — this is where blockages most commonly occur.

Flush with clean water and observe the drain rate.

Step 4: Hot Water and Degreaser (for Kitchen and Waste Water Drains)

For drains carrying kitchen or appliance waste water, grease is a primary cause of blockage. Treat with degreaser before moving to rodding:

1. Pour a kettle of boiling water into the gully pot (avoid boiling water in plastic gullies that may distort)
2. Add a generous amount of washing-up liquid or a dedicated drain degreaser
3. Wait 15 to 20 minutes for it to break down accumulated grease
4. Flush with cold water and test flow

For purely surface water drains collecting rainwater from gutters and patios, skip this step — degreaser will not help with leaf or silt blockages.

Step 5: Plunger or Drain Rods

If the gully is physically clear but the drain below it is still obstructed:

Use a plunger by submerging the cup in the gully and creating a firm seal against the outlet. Push and pull firmly and repeatedly. This shifts soft or partial blockages within the first metre or two of the underground pipe.

Use drain rods for blockages further down. Connect two or three rods and feed them carefully into the outlet at the bottom of the gully. Push gently toward the blockage and rotate clockwise to hook or break it up. Always rotate clockwise — anticlockwise rotation can unscrew the rod connections and leave them stuck in the pipe.

Step 6: When to Call a Professional for Jetting

Call a drainage company rather than continuing with DIY if:

• The blockage has not shifted after 20 to 30 minutes of rodding
• The drain clears but blocks again within days
• Sewage (not just surface water) is coming from the drain
• You can hear gurgling inside the property when using the outside drain
• Multiple drains are affected simultaneously
• You suspect the blockage is in the underground pipe beyond the gully

Professional high-pressure water jetting clears blockages that rods cannot reach, removes grease from pipe walls (not just the blockage), and prevents early recurrence. For drains that block repeatedly, a CCTV drain survey identifies root intrusion, collapsed pipes, or displaced joints causing the ongoing problem.

Yorkshire Water Blocked Drain: Who Is Responsible?

This is the question we are asked most frequently about outside drains — and the answer matters because it determines who pays for repairs.

Yorkshire Water maintains the public sewer network beneath roads and public land. If a public sewer is blocked or damaged, Yorkshire Water repairs it free of charge.

Your private drain — the pipes running within your property boundary and connecting your property to the public sewer — is your responsibility. Following changes to the Water Industry Act in 2011, many lateral drain connections (pipes running from individual properties to the public sewer, even where they run beneath public roads) transferred to Yorkshire Water's responsibility. However, drains within your garden and under your house remain private.

How to determine responsibility in practice:

• If only your property is affected, the fault is almost certainly on your private drain
• If multiple neighbouring properties are affected simultaneously, the fault may be in a shared private drain or the public sewer
• A CCTV drain survey locates the exact fault and provides a report to support a Yorkshire Water repair request if the fault proves to be on their network

Yorkshire Water's 24-hour emergency line — 0800 573 553 — handles flooding from public sewers and manholes overflowing in roads. For private drain problems affecting your property, you need a private drainage company. If you are unsure, call us — our engineers assess quickly and liaise with Yorkshire Water if the fault turns out to be on their network.

Outside Drain Blockages in Leeds: Common Patterns by Area

Tree-lined streets in Roundhay, Alwoodley, and Headingley — Autumn is the peak season for outside drain callouts across north Leeds. Surface water drainage designed for summer flow becomes overwhelmed as leaves decompose and mat together in gully pots. Clearing external gullies in September and October prevents many of the November blockage callouts we attend each year.

Wetherby and surrounding villages — Wetherby combines ageing clay pipes in the town centre with rural drainage in Boston Spa and Collingham. Outside drains in these villages sometimes back up with agricultural runoff during autumn and winter as field drainage saturates. Root intrusion from mature hedgerows is a secondary cause in older properties.

New-build estates in Garforth and south Leeds — Silt and builders' debris left in drain runs during construction causes outside drain problems in newer properties that have never worked properly. A professional jetting treatment followed by CCTV verification clears construction debris and confirms the drain route.

Get Help With a Blocked Outside Drain in Leeds

If DIY methods have not resolved your outside drain blockage, our engineers attend same day for urgent situations and within 24 hours for non-urgent bookings across Leeds and West Yorkshire. Every van carries jetting equipment and a CCTV camera.

Fixed price agreed before we start. No call-out fee. Request a quote online.